Aging Index, Lysosomal Enzyme Activities,and Meat Tenderness in Muscles from Electrically Stimulated Bull and Steer Carcasses

Correlations among biochemical indexes and muscle tenderness were evaluated in longissimus samples from bull and steer carcasses. Electrical stimulation increased carcass temperature,which was significantly (P<0.05) correlated with shear force, aging index, carcass pH pH, and microsomal and percentage free lysosomal enzyme activities. Aging index was not correlated with the decrease in carcass pH elicited by electrical stimulation.Meat from steer carcasses was more tender, displayed more negative aging indexes, and had greater soluble activities of glucuronidase and cathepsin B than meat from bull carcasses.     

Bacteriological Quality of Hot-Boned Primal Cuts from Electrically Stimulated Beef Carcasses

The objective of this study was to determine bacterial numbers on primal cuts from hot and cold-boned beef carcass sides, and to determine the influence of U.S. Grade and electrical stimulation of the cracass on the incidence of bacteria. Ten boneless primal cuts were removed from each of ten beef carcass sides either 1 or 48 hr after animal slaughter. The primal cuts included the brisket, clod, chuck roll, ribeye, striploin, tenderloin, top sirloin, knuckle, inside round, and gooseneck. The primal cuts were sampled for aerobic (APC 5°C, 20°, 35°C) and coliform bacteria at time of removal from the side and after 20 days' vacuum packaged storage at 2°C. The psychrotrophic bacteria enumerated at 5°C were more numerous (P<0.05) on the primals from the hot-boned sides than from the cold-boned sides before storage, but not after 20 days' storage at 2°C. The mesotrophic and psychrotrophic bacteria enumerated at 20°C, and the mesotrophic bacteria enumerated at 35°C, were more numerous on the hot-boned primals than on the cold boned primals both before and after storage (P<0.05). The magnitude of the difference, on some primals, was greater than one logarithm. Coliform bacteria were not influenced (P<0.05) by hot boning before or after storage. Storage of the primal cuts resulted in some profuse growth of the coliforms. Neither U.S. grade nor electrical stimulation had any apparent influence on the incidence or growth of aerobic bacteria.     

Microbiological Quality of Restructured and Conventional Steaks Manufactured from Electrically Stimulated Hot- and Cold-Boned Carcasses

The microbiological quality of restructured beef steaks was compared with that of conventional loin steaks. Restructured and conventional steaks were sampled before and after assignment to either a fresh meat overwrap (oxygen permeable) storage treatment for 1 wk or to vacuum packaged storage treatments for 1, 3 or 6 wk. Microbial counts were higher (P < 0.01) in restructured steaks than in conventional steaks. Except for Enterobacteriaceae and staphylococci counts, higher counts were observed for steaks from hot-boned sides than for steaks from cold-boned sides. Counts tended to be lower (P <0.01) for vacuum packaged steaks after 1 wk than for steaks packaged in oxygen permeable film. Aerobic, anaerobic, psychrotrophic, and lactobacilli counts increased (P < 0.01) for vacuum packaged steaks throughout the storage period.     

Properties of Frankfurters Made From Electrically Stimulated Beef

Frankfurters (3 replications of 4.54 kg meat batches) were conventionally made. Paired sides from beef were used for control (NES) and electrically stimulated (ES) meats (clods, flanks and plates). All-beef frankfurters (100% ES beef or 100% NES beef) and beef-pork frankfurters (80% ES beef-20% pork or 80% NES beef-20% pork) were made. The pork was not electrically stimulated. Proximate composition within cut of beef (plate, flank, clod) was not affected (P > 0.05) by ES. However, ES clods had (numerically) greater percentages of expressible juice loss, greater percentages of salt-soluble protein and lower percentages of juice loss during cooking than did NES clods (not statistically different). Use of ES beef alone or in combination with 20% pork did not affect external visual color, off-flavor, overall desirability or processing shrinkage of frankfurters. ES may affect certain properties (raw and cooked muscles) as measured in the laboratory, but when these ES muscles are used to make frankfurters, no real advantages or disadvantages were suggested by this study.     

Post-exsanguination Infusion of Ovine Carcasses: Effect on Tenderness Indicators and Muscle Microstructure

Lambs were assigned to 3 treatment groups: control (Ctr), infused with 10% volume (by wt) of a tenderizing blend (NCa), and NCa plus 0.015M CaCl₂ (WCa). Compared to Ctr and WCa, NCa-treated samples had lower shear force values (P < 0.05) and higher percent change in myofibrillar fragmentation index (P < 0.05). SDS-PAGE of infused samples revealed the appearance at 24 hr postmortem of 22-30 kd protein components. Scanning electron micrographs of NCa myofibrils showed they were more fragmented, fractured, or split and had wider interfibrillar spaces compared to Ctr and WCa. The fracture plane of muscles immediately postmortem was along the endomysial-sarcolemmal sheath, while at 24 hr postmortem the sheath was weakened enough for the fracture to occur along the surface of the myofibrils.     

Transaminase Affects Accumulation of Free Amino Acids in Electrically Stimulated Beef

Electrical stimulation (ES) of a beef carcass increases the content of free amino acids, which affects meat flavor. Levels of glutamic acid (Glu)-aminopeptidase activity were similar in both control and ES meat but decreased during storage to about 65% at 14 days. When 2-ketoglutaric acid (a substrate of transaminase) was added to the sarcoplasm, the level of Glu increased. Transaminase activity was unaffected by storage and was about 20% greater in ES than in the control. Transaminase activity in beef was confirmed when radioactive 2-ketoglutaric acid was added to the sarcoplasm. Results suggest that transaminase contributes to accumulation of some amino acids such as Glu in beef during conditioning.     

Electrical Stimulation of Mature Cow Carcasses and Its Effect on Tenderness, Myofibril Protein Degradation and Fragmentation

The effect of electrical stimulation was studied in the semi-membranosus, longissimus dorsi and triceps brachii of cow carcasses. Only one side of each carcass was stimulated (300V a.c., 120 sec). In each muscle, temperature, pH and myofibril fragmentation index (MF1) were measured and SDS-polyacrylamide gel electrophoresis performed at 0, 3, 6, 24, 72, and 168 hr post-stimulation while steaks for shear test were taken at 24, 72, and 168 hr. Electrical stimulation resulted in higher MF1, lower pH, higher temperature and lower shear force compared to the control but the time of appearance of the 30,000 dalton protein was not affected. Electrical stimulation improves tenderness by myofiber disrupture.     

Weight Loss and Sensory Attributes of Temperature Conditioned and Electrically Stimulated Hot Processed Pork

The effects of different electrical stimulation (ES) and conditioning systems on various attributes of postmortem pork muscle were investigated, using three hot boning systems (HB/11^oC–5 hr; HB; 17^oC– 3 hr; HB/ES– 1hr) and two cold boning systems (CB/controls; CB/ ES–24 hr). After each treatment, the cuts were vacuum packaged and chilled to 3^oC. The loin, top ham, bottom ham and knuckle of each were evaluated. Only the knuckle was not affected by processing treatment. The three hot boning systems produced cuts with significantly lower purge values in two-thirds of the cuts. CB/ES–24 hr resulted in high levels of purge, high cook losses and low sensory ratings for juiciness. Hot processed cuts were either equal to or superior to the conventionally processed cuts in every trait evaluated.     

植物乳杆菌和戊糖片球菌复合发酵牦牛肉工艺优化

酸化对鲜肉有一定的嫩化作用,利用植物乳杆菌和戊糖片球菌2 种益生菌复合发酵可以改善牦牛肉的嫩度。采用单因素试验和L9（34）正交试验设计,以pH值、剪切力和可溶性蛋白含量为评价指标,优化植物乳杆菌和戊糖片球菌复合发酵牦牛肉的工艺参数。结果表明：最佳工艺参数为发酵剂接种量1.0×106 CFU/g、发酵温度30 ℃、发酵时间18 h,在此条件下牦牛肉的pH值为5.02,剪切力为76.76 N,可溶性蛋白含量为52.02 mg/g。植物乳杆菌和戊糖片球菌复合发酵使牦牛肉的pH值降低,剪切力下降,可溶性蛋白含量增加,牦牛肉嫩度得到一定程度的改善。     

Considerations for Beef Tenderness Evaluations

SUMMARY: Data collected from 690 beef rib steaks were utilized to evaluate the methodology of beef tenderness measurements. The information obtained in this study was critically compared to existing research and evaluated in relation to sample handling procedures. Frozen storage of steaks, especially if they are unprotected from dehydration or are stored for long periods of time, has important implications if such data are to be compared to steaks which were evaluated in the unfrozen state. Cooking frozen steaks with or without thawing apparently has little effect on tenderness or cooking loss. Anatomical location of the sample should be carefully controlled to prevent spurious differences from affecting tenderness measurements. Evidence indicates that a tenderness gradient exists over the cross-section of the I. dorsi and suggests that core samples should be taken from as many and as varied positions as is feasible for existing research conditions. The use of marbling score as an indicator of the tenderness of beef rib steaks resulted in the explanation of 28 percent of the variation in average shear force requirements. The shear force value of the diaphragm muscle was only moderately related (r = 0.40) to that of the I. dorsi. Cooking loss percentages were significantly increased as a result of freezing at–34°C and storage of steaks unwrapped at −23°C when compared to unfrozen steaks and by selecting I. dorsi samples from more anterior locations in the wholesale rib.     

Concentration of Creatine Phosphate, Adenine Nucleotides and Their Derivatives in Electrically Stimulated and Nonstimulated Beef Muscle

The concentration of creatine phosphate (CP), adenosine tri-, di- and monophosphate (ATP, ADP and AMP, respectively), inosine monophosphate (IMP) and inosine in longissimus muscle removed from electrically stimulated (ES) and nonstimulated (NS) beef sides was enzymatically determined. After aging the carcass 7 days, steaks were removed for flavor evaluation. R values (absorbance ratios) were obtained from muscle samples removed over time from both sides. Data indicate more rapid catabolism of CP, ATP, and ADP in ES samples, with subsequent fluctuations in IMP and inosine concentration. At 12 and 24 hr post-stimulation, ES samples had more inosine; however, this difference did not exist after aging. Flavor differences were not observed after the 7-day aging period. R values parallel the degradation of adenine nucleotides and indicate rapid onset of rigor mortis in ES muscle.     

Time-Intensity Methodology for Beef Tenderness Perception

The Time-Intensity technique for measuring tenderness of bovine psoas major, longissimus dorsi, semitendinosus and shank was assessed. From the Time-Intensity curve, the Duration and area parameters (Increase and Decrease Area and Area Under the Curve) were most useful for sample separation. Using various Time-Intensity curve parameters, panelists were classified according to their perception of tenderness, with two clusters identified. A comparison of line scale results of force to chew and time to chew to the Time-Intensity results showed that comparable tenderness measurements were obtained by the two tests.     

Roasting vs Cooking in a Model System: Tenderness of Bull Adductor Muscle, Conventionally Chilled or Electrically Stimulated—Hot Boned

Conventionally chilled (CC) and electrically stimulated-hot boned (ESHB) bull adductor muscles roasted to 70° C, or muscle strips cooked in a model system (waterbath) to 70° C were compared. Sensory tenderness and texture (mealiness) and Instron texture characteristics were not affected significantly by the cooking system. Differences between carcass treatments (CC, ESHB) for sensory tenderness and texture were significant, but small. Percentage solubilized hydroxyproline did not have a major influence on sensory tenderness or texture, or on Instron texture characteristics of the muscle. Sensory tenderness and texture were related more to Instron cohesiveness and firmness than they were to Instron penetration measurements.     

Improved Tenderness of Restructured Beef Steaks by a Microbial Collagenase Derived from Vibrio B-30

To reduce connective tissue toughness Vibrio B-30 collagenase was evaluated for its ability to degrade muscle collagen in a restructured beef (RSB) product. Dissected muscles pooled from clods of 4 USDA choice chucks were made into three RSB products: untrimmed control (C), hand trimmed of epimysium (T) and untrimmed and treated with 0.01% collagenase (E). RSB products were held for 24 hr at either 2°C or 11°C and were analyzed cither raw or after heating (40°C for 1 hr). Aerobic microbial load remained low (1–2X10² cfu/g) during the 24 hr 11°C incubation. Heated samples of enzyme treated RSB had lower Lee-Kramer shear values than controls. In both raw and heated samples enzyme treatment increased hydroxyproline solubility. An enzyme treatment of 24 hr at 11°C followed by heating produced maximum tenderization. Although optimum treatment conditions need to be defined by further research, Vibrio B-30 collagenase appeared to be efficacious for the tenderization of RSB products.     

增加机械浆印刷纸的附加值提高市场竞争力

由于较高的性能（P）价格（C）比，机械浆印刷纸具有极大的竞争优势。利用有代表性的质量和成本参数来确定此性价比。通过测定适印性能参数来确定质量．而成本就是测定印刷纸的实际价值．以单位面积的美元或欧元表示。确定一个合理的．量化的P：C比值，了解增大该比值的方法，目的是提高现有的和潜在的机械浆印刷纸的竞争力。     

Trisodium Phosphate Treatment of Pork Carcasses

Pork skin samples, naturally contaminated or inoculated with Salmonella typhimurium, were treated with varying levels of trisodium phosphate (TSP). Aerobic plate counts (APC) of the samples were unaffected by treatment; however, S. typhimurium was reduced (P < 0.05). Using levels most effective for reducing S. typhimurium on skin, TSP was investigated for use on whole pork carcasses during slaughter/processing and did not affect APC of pork carcasses. Due to a lack of detectable presence, any effects of TSP on native Salmonella contamination of pork carcass surfaces could not be determined. TSP had negligible effect on visual pork color, texture or odor.     

Sampling Methods for Detection of Salmonella in Raw Chicken Carcasses

Detection of Salmonella in thaw water, pericloacal skin and whole carcass rinse samples from naturally contaminated broiler chickens was compared. Of 100 birds tested, 70 were found to contain salmonellae by the three sampling techniques combined; the median level of contamination was 0.27 salmonellae/100g eviscerated carcass weight. Recovery with the whole carcass rinse technique (93%) was significantly greater than that obtained with thaw water (63%) and skin (74%) methods; performance of the latter two methods was not statistically different. Thaw water does not provide a reliable index of Salmonella contamination and therefore is not a suitable method for the nondestructive analysis of poultry carcasses. Selective enrichment in tetrathionate brilliant green broth and plating on bismuth sulfite agar identified the greatest number of contaminated carcasses under all sampling conditions.     

Physical and Compositional Characteristics of Beef Carcasses Selected for Leanness

Ten muscles and muscle groups were excised from each of eight typical (average yield grade 2.99) and eight lean (average yield grade 1.73) steer carcasses and analyzed to determine differences between carcass types. Lean carcasses (raw basis) were higher (P<0.05) in moisture and protein and lower (P<0.05) in fat, cholesterol and calories in comparison to typical carcasses. Typical carcasses (cooked basis) were higher (P<0.05) in fat and caloric content than lean carcasses. No differences (P>0.05) were found between carcass types (cooked basis) for moisture, protein, cholesterol, dry matter cholesterol, cooking loss or shear force value. Semitendinosus muscles from typical carcasses were rated higher (P<0.05) for juiciness and tenderness than from lean carcasses. Differences (P<0.05) were found among muscles for all traits measured.